The present invention relates to a printing apparatus.
In recent years, some commercially available color page printers determine whether or not pages to be printed by an application on a host include any color, and when color is determined to be included, perform color printing using C (cyan), M (magenta), Y (yellow), and K (black) toner, whereas when no color is determined to be included, perform monochrome printing using only the K toner.
Meanwhile, some monochrome laser printers perform monochrome printing using K toner even when data intended for transmission to a color page printer for RGB full color printing are transmitted to the monochrome laser printer. Additionally, some color page printers are configured to operate as a monochrome page printer when C, M, and Y toner cartridges are not mounted thereon. When data for RGB full-color printing are transmitted to such a color page printer, because the color page printer is unable to perform color printing, the print data are discarded after being read.
The above described color page printer, which is configured to operate as a monochrome page printer when the C, M, and Y toner cartridges are not mounted, can perform the same monochrome printing using the K toner as that performed by a monochrome laser printer which performs monochrome printing using the K toner even when the data intended for transmission to a color page printer for RGB full-color printing are transmitted to the monochrome laser printer.
However, when such a printer as described above (i.e., a printer which performs monochrome printing in accordance with print data in which colors of the respective objects are specified by RGB values) is caused to print a document, or the like, in which some texts are assigned pale colors, a resultant printed matter involves a problem that the texts assigned pale colors are difficult or impossible to recognize. Similarly, when a document on which a graphic image in pale color is printed, the resultant printed matter involves a problem that the presence of the graphic image is difficult (or impossible) to recognize.
More specifically, the reason why an existing printer produces a monochrome printed matter in which texts/graphic images, to which pale colors are assigned, are difficult to recognize is that the existing printer obtains K values; that is, the amount of K toner used in printing, on the basis of RGB values specified in print data in accordance with below equations (1) and (2) (equations for obtaining a brightness from RGB values). Consequently, a printing amount of the K toner calculated from the RGB values for a pale color becomes small.gray=0.299R+0.587G+0.114B   (1)K=1.0−gray   (2)